Journal of Applied Physiology, Vol 50, Issue 5 1027-1035, Copyright © 1981 by American Physiological Society
Effects of intrapleural pressure changes on canine left ventricular function
W. B. Wead and J. F. Norton
Left ventricular diameter, pressure, and dP/dt, as well as aortic and
intrapleural pressures, were recorded simultaneously from 10 acute
anethetized mongrel dogs. Normal inspiration produced a significant
decrease in end-diastolic diameter (46.9 +/- 1.2 to 43.1 +/- 1.0 mm) and
end-systolic diameter (35.5 +/- 1.4 to 34.2 +/- 1.7 mm), reducing stroke
diameter 2.5 mm. Airway occlusion (greater than or equal to 60%) produced a
reduction in the decrease of end-diastolic diameter seen with normal
inspiration and, to a lesser degree, in end-systolic diameter. Because only
acute airway occlusion greater than or equal to 80% produced a significant
increase in left ventricular afterload, the authors conclude that normal
spontaneous inspiration results in a decrease in left ventricular preload
due to pooling of blood in the pulmonary vasculature. The data suggest that
this decrease in left ventricular preload is the predominant mechanism
responsible for the inspiratory decrease in left ventricular stroke volume.
